A Model of the Oxidation of Polycyclic Aromatic Compounds in Cloud and Fog Droplets

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Monday, 5 January 2015
Jershon Dale Eagar, Arizona State University, Tempe, AZ; and P. Herckes and B. Ervens

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the atmosphere. PAHs are oxidized in the atmosphere to produce (among other species) oxy-PAHs or PAHs with one or more oxygen atoms. The role of clouds and fogs and their influence on the abundance of oxy-PAHs in the atmosphere have been previously studied. This work presents a computer model that predicts PAH reaction and oxy-PAH / PAH partitioning in the suspended droplet phase in the atmosphere. A FORTRAN model that had previously been used for modeling non-aromatic species was adapted to PAH and oxy-PAH. Concentrations of PAH and oxy-PAH comparable to those reported in fogs and clouds were used. Partitioning between the droplet and gas phases was investigated with calculated Henry's law constants, octanol-air partition coefficients, and octanol-water partition coefficients. Literature photooxidation rates were incorporated for PAH loss. The production of oxy-PAH was modeled using experimentally determined rates in simulated solar irradiation. This work builds upon prior research by calculating the loss of PAH species and gain of oxy-PAH in a representative cloud and fog droplet.